Leftists need to focus more on being understood by the average person. Redefining words and trying to take back redefined words doesn't help that cause though I make an exception for "The Left" "Leftist/ism" etc.

Shouldn't anarchists be taking the word "libertarian" back from ancaps and other propertarians?

Yes, lets, wherever that's happened. Some places have not suffered this usurpation and perversion of language.